Nucleic acids may typically be manipulated in aqueous solution and may generally be associated with metal cations. For example, compositions of DNA may typically contain alkali metal countercations that render DNA a crystalline solid that is soluble only in water.
In Gerald S. Manning, et al., “The Molecular Theory of Polyelectrolyte Solutions with Applications to the Electrostatic Properties of Polynucleotides”, Quarterly Review of Biophysics II, 2:179–246 (1978), the authors discuss binding of various cationic substances with DNA in an aqueous environment. These cationic substances include metal cations, small cations with complex structures such as oligolysine and spermine, as well as high-molecular-weight cations such as polylysine.
In M. Thomas Record, et al., “Thermodynamic Analysis of Ion Effects on the Binding and Conformational Equilibria of Proteins and Nucleic Acids: The Roles of Ion Association or Release, Screening, and Ion Effects on Water Activity”, Quarterly Review of Biophysics II, 2:103–178 (1978), the authors discuss the various effects of low-molecular-weight electrolytes in the associations and interactions of proteins and nucleic acids.
In Enders Dickinson, V, et al., “Hybrid Redox Polyether Melts Based on Polyether-Tailed Counterions”, J. Am. Chem. Soc. 121:613–616 (1999), the authors propose transforming various ionic materials into room temperature molten salts by combining them with polyether-tailed counter ions such as polyether-tailed 2-sulfobenzoate and polyether-tailed triethylammonium. The ionic materials include ruthenium hexamine, metal trisbipyridines, metal trisphenanthrolines, and ionic forms of aluminum quinolate, anthraquinone, phthalocyanine, and porphyrins. The authors do not describe transforming nucleic acids into molten salts.
In Mary Elizabeth Williams, et al., “Electron and Mass Transport in Hybrid Redox Polyether Melts: Co and Fe Bipyridines with Attached Polyether Chains”, J. Am. Chem. Soc., 119: 1997–2005 (1997), the authors discuss how to discern charge transport by electron self exchange reactions from transport by physical diffusion so as to measure electron transfer rate constants in a series of undiluted metal complex molten salts [M(bpy(CO2MePEG)2)3]+ (ClO4)2− where M=Co(II/I) and Fe(III/II) and MePEG is an oligomeric polyether of MW 150, 350, and 550 (the cation portion of which is shown below). In Enders Dickinson V, et al., “The Effect of Polyether Attachment on the Self-Exchange Barriers of Metal Tris(bipyridine) Molten Salts”, J. Phys. Chem., 103:11028–11035 (1999), the authors propose highly viscous, room temperature molten salts that may be obtained by associating [M(bpy)3]2+ cations (where M=Ru or Co and bpy=2,2′-bipyridine) with polyether-tailed 2-sulfobenzoate anions. These articles do not discuss molten salts of nucleic acids, nor do the authors appear to recognize the benefits of forming redox-active melts where both the cation and the anion may be capable of electron transfer.
In Yoshio Okahata, et al., “Anisotropic Electric Conductivity in an Aligned DNA Cast Film”, J. Am. Chem. Soc., 120: 6165–6166 (1998), the authors propose an aligned DNA film as an anisotropic conductive film, in which counter Na+ cations were exchanged completely to cationic amphiphiles. The authors report that the aligned DNA film was prepared as follows. An aqueous solution of DNA from Salmon testes (average MW 1.3×106, ca. 2000 bp) was mixed with an aqueous solution of a cationic amphiphile, N,N,N-trimethyl-N-(3,6,9,12-tetraoxadocosyl) ammonium bromide, (CH3)3N(CH2CH2O)4(CH2)9(CH3)+Br−. The precipitate DNA-lipid polyion complex (1:1 ratio of phosphate anion to cationic amphiphile) was collected and solubilized in chloroform/ethanol (4:1 v/v). The solution (40 mg/mL, 4 wt %) was cast on a Teflon plate, and the solvent was evaporated slowly under saturated solvent vapor at room temperature. The obtained self-standing film (ca. 60 microns thick) was transparent, flexibly strong, and water-insoluble. The reference does not propose molten salts of polynucleic acids that are liquid. Furthermore, the precipitated DNA-lipid polyanion complex discussed by the authors is not soluble in water.
Various references have discussed the possibility of electron transport through DNA. For example, in Danny Porath, et al., “Direct Measurement of Electrical Transport Through DNA Molecules”, Nature, 403: 635–638 (2000), the authors present measurements of electrical transport through individual 10.4 nm-long, double-stranded poly(G)-poly(C) DNA molecules connected to two metal nanoelectrodes, that may indicate large-bandgap semiconducting behavior. In Frederick D. Lewis, et al., “Distance-Dependent Electron Transfer in DNA Hairpins”, Science, 277: 673–676 (1997), the authors discuss the distance dependence of photoinduced electron transfer in duplex DNA, and state that while kinetic analysis suggests that duplex DNA is somewhat more effective than proteins as a medium for electron transfer, it does not function as a molecular wire. In Joshua Jortner, et al., “Charge Transfer and Transport in DNA”, Proc. Natl. Acad. Sci., 95: 12759–12765 (1998), the authors explore charge migration in DNA and advance two distinct mechanisms of charge separation in a donor-bridge-acceptor system. In Daniel B. Hall, et al., “Oxidative DNA Damage Through Long-range Electron Transfer”, Nature, 382: 731–735 (1996), the authors note that the DNA double helix, which contains a π-stacked array of heterocyclic base pairs, could be a suitable medium for the migration of charge over long molecular distances. In Hans-Werner Fink & Christian Schonenberger, “Electrical Conduction Through DNA Molecules”, Nature, 398: 407–410 (1999), the authors report direct measurements of electrical current as a function of the potential applied across a few DNA molecules associated into single ropes at least 600 nm long, which indicate effective conduction through the ropes. In Gary B. Schuster, “Long-Range Charge Transfer in DNA: Transient Structural Distortions Control the Distance Dependence, Acc. Chem. Res., 33: 253–260 (2000), the author proposes a mechanism for long-range charge transport in DNA that depends on its spontaneous structural distortion. This mechanism is referred to as phonon-assisted polaron hopping. In Frederick D. Lewis, et al., “Direct Measurement of Hole Transport Dynamics in DNA”, Nature, 406: 51–53 (2000), the authors propose that electrons and holes can migrate from the locus of formation to trap sites, and such migration can occur through either a single step “super exchange” mechanism or a multistep charge transport “hopping” mechanism. These references do not describe molten salts of nucleic acids, and do not suggest how to obtain such molten salts.
Several authors have proposed the use of nucleic acids in molecular electronics. For example, in Robert Elghanian, et al., “Selective Colorimetric Detection of Polynucleotides Based on the Distance-Dependent Optical Properties of Gold Nanoparticles”, Science, 277: 1078–1081 (1997), the authors discuss the use of nucleic acids to form a polymeric network of nanoparticles. In Chad A Mirkin, “Programming the Assembly of Two- and Three-Dimensional Architectures with DNA and Nanoscale Inorganic Building Blocks”, Inorg. Chem., 39:2258–2272 (2000), the author discusses the development of biological-based methods for directing the assembly of nanoscale inorganic building blocks into functional materials. The author proposes using DNA as a synthetically programmable assembler. In J. J. Hopfield, et al., “A Molecular Shift Register Based on Electron Transfer”, Science, 241: 817–820 (1988), the authors propose an electronic shift-register memory at the molecular level. The authors mention that one scheme to build such a register may take advantage of the linear structure of DNA to which sequence-specific chromophore-bearing groups could be bound. However, methods for carrying out such a scheme are not provided. In Leonard M. Adelman, “Molecular Computation of Solutions to Combinatorial Problems”, Science, 266: 1021–1024 (1994), the author proposes carrying out computations at the molecular level using the tools of molecular biology to solve an instance of the directed Hamiltonian path problem. A small graph was encoded in molecules of DNA, and the “operations” of the computation were performed with standard protocols and enzymes. In Michael C. Pirrung, et al., “The Arrayed Primer Extension Method for DNA Microchip Analysis: Molecular Computation of Satisfaction Problems”, J. Am. Chem. Soc., 122: 1873–1882 (2000), the authors discuss a DNA computer which may be capable of solving nondeterministic polynomial time (NP)-complete problems (those whose time-complexity function rises exponentially with the problem size) in polynomial time using an arrayed primer extension method. These methods are based on template-dependent extension of DNA primers bound to a solid phase with a labeled dideoxyribonucleotide terminator, followed by detection of the label so added. These references do not describe molten salts of nucleic acids, nor do they appear to recognize the usefulness of such molten salts in molecular electronic applications.